Journal of Vestibular Research - Volume 18, issue 5-6

Authors: Isableu, Brice | Gueguen, Marc | Fourré, Benoît | Giraudet, Guillaume | Amorim, Michel-Ange

Article Type: Research Article

Abstract: The identification of subject’s perceptual style regarding multisensory integration is a central issue for spatial perception and sensorimotricity. In spatial orientation studies, the weighting of visual frame of reference (visual field dependence) is classically assessed by using verticality perception tasks, and especially the mechanical 3D rod-and-frame test (3D RFT). The validation of a 2D computer-based version of the RFT by virtue of its portability would facilitate the identification of modes of spatial referencing for the design and evaluation of sensory and motor rehabilitation programs. We question here whether the computerized 2D RFT yields frame effects similar (in amplitude, direction) and …correlated to those induced by the mechanical 3D RFT. In both devices, 35 young and healthy males’ subjects were seated and tasked with aligning a rod to the gravity vertical within a square frame that was tilted at 18Âř. The results showed significantly larger rod deviations from the verticality in the 3D RFT. 3D and 2D RFT errors significantly correlated but shared a small amount of common variance (r 2 = 0.35 ). In addition, left-right tilt asymmetry changes from one device to another. These results suggest that the mechanical 3D RFT for verticality perception remains a more robust test for identifying the subject’s perceptual style. Show more

Keywords: Computers, rod-and-frame test, spatial perception, verticality, visual field dependence-independence, frames of reference

DOI: 10.3233/VES-2008-185-601

Citation: Journal of Vestibular Research, vol. 18, no. 5-6, pp. 239-247, 2008

Authors: Holly, Jan E. | McCollum, Gin

Article Type: Research Article

Abstract: This review focusses attention on a ragged edge of our knowledge of self-motion perception, where understanding ends but there are experimental results to indicate that present approaches to analysis are inadequate. Although self-motion perception displays processes of "top-down" construction, it is typically analyzed as if it is nothing more than a deformation of the stimulus, using a "bottom-up" and input/output approach beginning with the transduction of the stimulus. Analysis often focusses on the extent to which passive transduction of the movement stimulus is accurate. Some perceptual processes that deform or transform the stimulus arise from the way known properties of …sensory receptors contribute to perceptual accuracy or inaccuracy. However, further constructive processes in self-motion perception that involve discrete transformations are not well understood. We introduce constructive perception with a linguistic example which displays familiar discrete properties, then look closely at self-motion perception. Examples of self-motion perception begin with cases in which constructive processes transform particular properties of the stimulus. These transformations allow the nervous system to compose whole percepts of movement; that is, self-motion perception acts at a whole-movement level of analysis, rather than passively transducing individual cues. These whole-movement percepts may be paradoxical. In addition, a single stimulus may give rise to multiple perceptions. After reviewing self-motion perception studies, we discuss research methods for delineating principles of the constructed perception of self-motion. The habit of viewing self-motion illusions only as continuous deformations of the stimulus may be blinding the field to other perceptual phenomena, including those best characterized using the mathematics of discrete transformations or mathematical relationships relating sensory modalities in novel, sometimes discrete ways. Analysis of experiments such as these is required to mathematically formalize elements of self-motion perception, the transformations they may undergo, consistency principles, and logical structure underlying multiplicity of perceptions. Such analysis will lead to perceptual rules analogous to those recognized in visual perception. Show more

DOI: 10.3233/VES-2008-185-602

Citation: Journal of Vestibular Research, vol. 18, no. 5-6, pp. 249-266, 2008

Authors: Ishida, Masayuki | Fushiki, Hiroaki | Nishida, Hiroshi | Watanabe, Yukio

Article Type: Research Article

Abstract: Self-motion is known to be falsely perceived during exposure to the movement of visual surroundings. This illusory perception of visually-induced self-motion is known as "vection." The present study was conducted to examine the relative strengths of vection versus whole-body angular acceleration as they determine perceived self-rotation under conditions in which they individually provide conflicting information. Each subject was rotated for 90 s about a vertical axis at a constant acceleration, and a large-field visual surround in front of the subject was simultaneously rotated at a constant acceleration in the same direction, but at a magnitude of acceleration twice that of …the body. This stimulus condition creates a sensory conflict between information from the vestibular/somatosensory systems and information from the visual system with respect to the direction of self-rotation. The subject eventually perceived self-acceleration in the direction of circular vection (CV), even though he or she was actually being accelerated in the direction opposite to CV. When the magnitude of contradictory chair acceleration exceeded the vestibular perceptual threshold, the onset latency of CV was significantly delayed. Our results suggest that visual information contributes to the perception of self-acceleration, and that illusory self-motion could overwhelm the feeling of self-acceleration due to inertial motion. CV would thus be a significant factor in determining spatial orientation in certain operational environments and flight conditions. Show more

Keywords: Virtual environment, motion sickness, spatial orientation, visual-vestibular interaction

DOI: 10.3233/VES-2008-185-603

Citation: Journal of Vestibular Research, vol. 18, no. 5-6, pp. 267-272, 2008

Authors: Sienko, K.H. | Balkwill, M.D. | Oddsson, L.I.E. | Wall, C.

Article Type: Research Article

Abstract: Single-axis vibrotactile feedback of trunk tilt provided in real-time has previously been shown to significantly reduce the root-mean-square (RMS) trunk sway in subjects with vestibular loss during single-axis perturbation. This research examines the effect of multi-directional vibrotactile feedback on postural sway during continuous multi-directional surface perturbations when the subjects' eyes are closed. Eight subjects with vestibular loss donned a multi-axis feedback device that mapped body tilt estimates onto their torsos with a 3-row by 16-column array of tactile actuators (tactors). Tactor row indicated tilt magnitude and tactor column indicated tilt direction. Root-mean-square trunk tilt, elliptical fits to trunk sway trajectory …areas, percentage of time spent outside a no vibrotactile feedback zone, RMS center of pressure, and anchoring index parameters indicating intersegmental coordination were used to assess the efficacy of the multi-directional vibrotactile balance aid. Four tactor display configurations in addition to the tactors off configuration were evaluated. Subjects had significantly reduced RMS trunk sway, significantly smaller elliptical fits of the trajectory area, and spent significantly less time outside of the no feedback zone in the tactors on versus the tactors off configuration. Among the displays evaluated in this study, there was not an optimal tactor column configuration for standing tasks involving continuous surface perturbations. Furthermore, subjects performed worse when erroneous information was displayed. Therefore, a spatial resolution of 90° (4 columns) seems to be as effective as a spatial resolution of 22.5° (16 columns) for control of standing. Show more

Keywords: Vibrotactile, balance prosthesis, biofeedback, balance, intuitive display

DOI: 10.3233/VES-2008-185-604

Citation: Journal of Vestibular Research, vol. 18, no. 5-6, pp. 273-285, 2008

Authors: Guzy, Lawrence T. | Albery, William B. | Goodyear, Chuck

Article Type: Research Article

Abstract: The vestibular system by itself is incapable of effectively compensating for the graveyard spin illusion. We examined two countermeasures, i.e., efficacy of vibrotactile stimulation around the waist and virtual 3-D audio presented independently and jointly for controlling a simulated graveyard spin. We also examined: a) additional training with these countermeasures to improve "intuitiveness;" b) included non-perturbation trials along with perturbation trials; and c) monitored changes in well-being as measured by a motion sickness scale from pre- to post-test and immediately following each trial. Ten volunteers received two training and two test sessions. The somatogyral illusion was generated by accelerating a …chair for 24 s until it attained a peak rotation of 120°/s and then stopped. Over the ensuing 40 s the chair rotated in one of two random perturbation patterns or remained stationary. During this period, participants were required to eliminate all movements of the chair by turning a knob in the opposite direction of perceived rotation. For the control trials, participants relied solely on vestibular signals to cancel perceived movements. For the experimental trials, vibrotactile stimulation around the waist, virtual 3-D audio, or both were presented. The mean Cancellation Error (CE) for the control trials was 52°/s. The application of the countermeasures significantly reduced the CE. Additional training and testing did not improve intuitiveness. Perturbations to the chair resulted in a higher CE than no perturbations. Motion sickness symptoms showed no differences from pre- to post-test and very rarely reported after each trial. Show more

Keywords: Spatial disorientation, virtual stereo sound, rotating chair, angular yaw motion, motion perception, cancellation error

DOI: 10.3233/VES-2008-185-605

Citation: Journal of Vestibular Research, vol. 18, no. 5-6, pp. 287-294, 2008

Authors: Cohen, Helen S. | Kimball, Kay T.

Article Type: Research Article

Abstract: The goal of this study was to determine which of several clinical balance tests best identifies patients with vestibular disorders. We compared the scores of normals and patients on the Berg Balance Scale (Berg), Dynamic Gait Index (DGI), Timed Up and Go (TUG), Computerized Dynamic Posturography Sensory Organization Test (SOT), and a new obstacle avoidance test: the Functional Mobility Test (FMT). The study was performed in an out-patient balance laboratory at a tertiary care center. Subjects were 40 normal adults, and 40 adults with vestibular impairments. The main outcome measures were the sensitivity of tests to patients and specificity to …normals. When adjusted for age the Berg, TUG, DGI and FMT had moderate sensitivity and specificity. SOT had moderately high sensitivity and specificity. SOT and FMT, combined, had high sensitivity and moderate specificity. Therefore, the kinds of tests of standing and walking balance that clinicians may use to screen patients for falling are not as good for screening for vestibular disorders as SOT. SOT combined with FMT is better. When screening patients for vestibular disorders, when objective diagnostic tests of the vestibular system, itself, are unavailable, tests of both standing and walking balance, together, give the most information about community-dwelling patients. These tests may also indicate the presence of sub-clinical balance problems in community-dwelling, asymptomatic adults. Show more

Keywords: Dizziness, balance, posture, vestibular function tests, obstacle avoidance

DOI: 10.3233/VES-2008-185-606

Citation: Journal of Vestibular Research, vol. 18, no. 5-6, pp. 295-303, 2008